Optical scanning unit and electro-photographic image forming apparatus including the same

Abstract

An optical scanning unit that includes a first optical device that forms collimated light from light radiated from a light source, a second optical device that focuses the collimated light onto a deflector, and an imaging optical device that focuses light deflected by the deflector onto an exposure object. The optical scanning unit further includes a refraction unit and a diffraction unit, and the power of the refraction unit is φr, the power of the diffraction unit is φd, and the ratio φr/φd is such that 0.5<φr/φd<1.3.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of Korean Application No. 2007-50999, filed May 25, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by referenceBACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]Aspects of the present invention relate to an optical scanning unit and an electro-photographic image forming apparatus that employs the same.[0004]2. Description of the Related Art[0005]An electro-photographic image forming apparatus includes an optical scanning unit that scans light modulated in response to image information, to a photosensitive body (exposure object), and deflects the light in a main scanning direction using a deflector, such as a polygon mirror. The optical scanning unit includes a collimating lens, a cylindrical lens, and an fθ lens, in order to focus light radiated from a light source, onto a photosensitive body. Refractive indexes of the above lenses vary acco...

AI Technical Summary

Benefits of technology

[0006]To solve the above and / or other problems, aspects of the present invention provide an optical scanning unit, which can compensate for temperature changes and thereby prevent focus movement, and an electro-photographic image forming apparatus that employs the optical scanning unit.

Problems solved by technology

Refractive indexes of the above lenses vary according to temperature, and such variations may cause focus movement.

For example, the light radiated from the light source may not be accurately focused on the photosensitive body.

If focus movement occurs, the light may be improperly focused onto a photosensitive body, thereby reducing the quality of printed images formed by the photosensitive body.

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